This invention relates to a cathode ray tube device of a preheated cathode type including a cathode ray tube and an electric circuit to operate the tube.
In a conventional cathode ray tube device of such a type, an electron beam emitted from a heated cathode has been kept in a cut-off state during a waiting time, by suppling a certain voltage to the first grid of an electron gun assembly. Upon the starting of the cathode ray tube, the cut-off state is released to rapidly start the cathode ray tube in a stable condition. The maintenance of such a cut-off state causes the cathode to be deteriorated, resulting in the shorter life time.